The panel is definitely a factory fitted thing, welded to the firewall at the front and to the skin panel at the bottom. It floats about 1/2 inch at the top, presumably to provide stiffness, possibly for the windscreen pillar itself...
Can other bugeye owners please check if they have this panel, see pic in my previous post.
It's in an awkward location - a stretch for my old neck to get down there, and it was particuarly arduous to get the camera in there and focused correctly - but the resulting pic was very good. Full marks to the Canon Digital Rebel XT!!!